How fast should a 6500a rip?

I got it with my inspiron 8600 with 8x dvd DL (which until the media comes down wont get used) and updated the firmware with the liggy 2.23 and was wondering what type of rip speeds i should expect, ive gotten about 3.9x as the tops, shouldnt it be faster? its better than Stock which seemed about 2x ~3x. Something im doing wrong or just as fast as she goes (which then i might need my old hitachi which did 5-9x)